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Cisco IOS Interface Command Reference, Release 12.1
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About the Cisco IOS Software Documentation
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Using Cisco IOS Software
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Interface Commands - Introduction
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Interface Commands (access-list - cut-through)
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Interface Commands (dce-terminal-timing enable - interface)
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Interface Commands (interface fastethernet - loopback line)
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Interface Commands (loopback remote - service-module t1 remote-loopback)
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Interface Commands (service-module t1 timeslots - show hub)
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Interface Commands (show interfaces - show interfaces vg-anylan)
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Interface Commands (show pas caim - tx-queue-limit)
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Index
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Table Of Contents
service-module 56k clock source
service-module 56k data-coding
service-module 56k network-type
service-module 56k remote-loopback
service-module 56k switched-carrier
service-module t1 clock source
service-module t1 remote-alarm-enable
service-module t1 remote-loopback
loopback remote (interface)
To loop packets through a CSU/DSU, over a DS-3 link or a channelized T1 link, to the remote CSU/DSU and back, use the loopback remote interface configuration command. To remove the loopback, use the no form of this command.
FT1/T1 CSU/DSU Modules
loopback remote {full | payload | smart-jack} [0in1 | 1in1 | 1in2 | 1in5 | 1in8 | 3in24 | qrw | user-pattern 24bit-binary-value]
no loopback remote {full | payload | smart-jack}
2- and 4-Wire, 56/64-kbps CSU/DSU Modules
loopback remote [2047 | 511 | stress-pattern pattern-number]
no loopback remote
Syntax Description
Defaults
Disabled
Command Modes
Interface configuration
Command History
Usage Guidelines
This command applies only when the remote CSU/DSU device is configured for this function. It is used for testing the data communication channels along with or without remote CSU/DSU circuitry. The loopback is usually performed at the line port, rather than the DTE port, of the remote CSU/DSU.
For a multiport interface processor connected to a network via a channelized T1 link, the loopback remote interface configuration command applies if the remote interface is served by a DDS line (56 kbps or 64 kbps) and the device at the remote end is a CSU/DSU. In addition, the CSU/DSU at the remote end must react to latched DDS CSU loopback codes. Destinations that are served by other types of lines or that have CSU/DSUs that do not react to latched DDS CSU codes cannot participate in an interface remote loopback. Latched DDS CSU loopback code requirements are described in AT&T specification TR-TSY-000476, "OTGR Network Maintenance Access and Testing."
For the integrated FT1/T1 CSU/DSU module, the loopback remote full command sends the loopup code to the remote CSU/DSU. The remote CSU/DSU performs a full-bandwidth loopback through the CSU portion of the module. The loopback remote payload command sends the loopup code on the configured timeslots, while maintaining the D4-Extended Super Frame. The remote CSU/DSU performs the equivalent of a loopback line payload request. The remote CSU/DSU loops back only those timeslots that are configured of the remote end. This loopback reframes the data link, regenerates the signal, and corrects bi polar violations and extended super frame CRC errors. The loopback remote smart-jack command sends a loopup code to the remote smart jack. You cannot put the local smart jack into loopback.
Failure to loopup or initiate a remote loopback request could be caused by enabling the no service-module t1 remote-loopback command or having an alternate remote-loopback code configured on the remote end. When the loopback is terminated, the result of the pattern test is displayed.
For the 2- and 4-wire, 56/64-kbps CSU/DSU module, an active connection is required before a loopup can be initiated while in switched mode. When transmitting V.54 loopbacks, the remote device is commanded into loopback using V.54 messages. Failure to loopup or initiate a remote loopback request could be caused by enabling the no service-module 56k remote-loopback command.
To show interfaces currently in loopback operation, use the show interfaces loopback EXEC command.
Examples
The following example configures a remote loopback test:
Router(config)#interface serial 0 Router(config-if)#loopback remoteThe following example configures the remote device into full-bandwidth line loopback while specifying the qrw test pattern over the T1 CSU/DSU module on a Cisco 2524 or Cisco 2525 router:
Router(config)#interface serial 0Router(config-if)#loopback remote full qrwRouter(config-if)#%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to down%LINK-3-UPDOWN: Interface Serial0, changed state to down%SERVICE_MODULE-5-LOOPUPREMOTE: Unit 0 - Remote unit placed in loopbackThe following example transmits a remote loopback stress pattern over the 4-wire, 56/64-kbps CSU/DSU module, which tests the stress clocking of the network:
Router(config-if)#loopback remote stress-pattern 1Router(config-if)#%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1, changed state to down%LINK-3-UPDOWN: Interface Serial1, changed state to down%SERVICE_MODULE-5-LOOPUPREMOTE: Unit 1 - Remote unit placed in loopbackRelated Commands
mdl
To configure the Maintenance Data Link (MDL) message defined in the ANSI T1.107a-1990 specification for the CT3 in a Cisco AS5800 universal access server, or for the CT3IP in Cisco 7500 series routers, use the mdl interface configuration command. To remove the message, use the no form of this command.
mdl {transmit {path | idle-signal | test-signal} | string {eic | lic | fic | unit | pfi | port | generator} string}
no mdl {transmit {path | idle-signal | test-signal} | string {eic | lic | fic | unit | pfi | port |generator} string}
Syntax Description
Defaults
No MDL message is configured.
Command Modes
Interface configuration
Command History
Usage Guidelines
Use the show controllers t3 command to display MDL information (received strings). MDL information is displayed only when framing is set to C-bit.
Note
MDL is supported only when the DS3 framing is C-bit parity.
Examples
The following examples show several of the mdl commands for the CT3IP in slot 9:
Router(config)# controller t3 9/0/0Router(config-controller)# mdl string eic Router ARouter(config-controller)# mdl string lic Test NetworkRouter(config-controller)# mdl string fic Building BRouter(config-controller)# mdl string unit ABCRelated Commands
media-type
To specify the physical connection on an interface, use the media-type interface configuration command. To restore the default value, use the no form of this command.
media-type {aui | 10baset | 100baset | mii}
no media-type {aui | 10baset | 100baset | mii}
Syntax Description
Defaults
AUI 15-pin physical connection is the default setting on Cisco 4000 series routers.
100BaseT physical connection is the default setting on Cisco 7000 series and Cisco 7200 series routers.
Command Modes
Interface configuration
Command History
Usage Guidelines
To specify the physical connection on an interface, use the following interface configuration:
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•
•
Examples
The following example selects an RJ-45 10BaseT physical connection on Ethernet interface 1:
Router(config)# interface ethernet 1Router(config-if)# media-type 10basetThe following example specifies a media-independent interface physical connection to Fast Ethernet slot 0, port 1 on the Cisco 7000 or 7200 series:
Router(config)# interface fastethernet 0/1Router(config-if)# media-type miiThe following example specifies a media-independent interface physical connection to Fast Ethernet slot 0, port adapter 1, port 1 on the Cisco 7500 series:
Router(config)# interface fastethernet 0/1/1Router(config-if)# media-type miimedia-type half-duplex
The half-duplex command replaces this command.
modem dtr-delay
To control the time that a data terminal ready (DTR) signal is held down when a line clears, use the modem dtr-delay line configuration command. To restore the default hold down time, use the no form of this command.
modem dtr-delay seconds
no modem dtr-delay seconds
Syntax Description
Defaults
The default DTR signal hold down time is 5 seconds.
Command Modes
Line configuration
Command History
Usage Guidelines
Use this command to reduce the time that a DTR signal is held down after an asynchronous line clears and before the DTR signal is raised again to accept new calls. Incoming calls may be rejected in heavily loaded systems even when modems are unused because the default DTR hold down interval may be too long. The modem dtr-delay command is designed for lines used for an unframed asynchronous session such as Telnet. Lines used for a framed asynchronous session such as PPP should use the pulse-time interface command.
Examples
The following example shows how to specify a DTR hold down interval of 2 seconds:
Router(config)# line 7Router(config-line)# modem dtr-delay 2Related Commands
mop enabled
To enable an interface to support the Maintenance Operation Protocol (MOP), use the mop enabled interface configuration command. To disable MOP on an interface, use the no form of this command.
mop enabled
no mop enabled
Syntax Description
This command has no arguments or keywords.
Defaults
Enabled on Ethernet interfaces and disabled on all other interfaces.
Command Modes
Interface configuration
Command History
Examples
The following example enables MOP for serial interface 0:
Router(config)# interface serial 0Router(config-if)# mop enabledRelated Commands
mop sysid
To enable an interface to send out periodic Maintenance Operation Protocol (MOP) system identification messages, use the mop sysid interface configuration command. To disable MOP message support on an interface, use the no form of this command.
mop sysid
no mop sysid
Syntax Description
This command has no arguments or keywords.
Defaults
Enabled
Command Modes
Interface configuration
Command History
Usage Guidelines
You can still run MOP without having the background system ID messages sent. This command lets you use the MOP remote console, but does not generate messages used by the configurator.
Examples
The following example enables serial interface 0 to send MOP system identification messages:
Router(config)# interface serial 0Router(config-if)# mop sysidRelated Commands
mop device-code
Identifies the type of device sending MOP sysid messages and request program messages.
Enables an interface to support the MOP.
mtu
To adjust the maximum packet size or maximum transmission unit (MTU) size, use the mtu interface configuration command. To restore the MTU value to its original default value, use the no form of this command.
mtu bytes
no mtu
Syntax Description
Defaults
Table 13 lists default MTU values according to media type.
Table 13 Default Media MTU Values
Ethernet
1500
Serial
1500
Token Ring
4464
ATM
4470
FDDI
4470
HSSI (HSA)
4470
Command Modes
Interface configuration
Command History
Usage Guidelines
Each interface has a default maximum packet size or MTU size. This number generally defaults to the largest size possible for that type interface. On serial interfaces, the MTU size varies, but cannot be set smaller than 64 bytes.
Caution
%RSP-3-Restart:cbus complex.
Protocol-Specific Versions of mtu Command
Changing the MTU value with the mtu interface configuration command can affect values for the protocol-specific versions of the command (the ip mtu command, for example). If the value specified with the ip mtu interface configuration command is the same as the value specified with the mtu interface configuration command, and you change the value for the mtu interface configuration command, the ip mtu value automatically matches the new mtu interface configuration command value. However, changing the values for the ip mtu configuration commands has no effect on the value for the mtu interface configuration command.
ATM and LANE Interfaces
ATM interfaces are not bound by what is configured on the major interface. By default, MTU on a subinterface is equal to the default MTU (4490); if a client is configured the default is 1500. MTU can be changed on subinterfaces, but it may result in recarving of buffers to accommodate the new maximum MTU on the interface.
Examples
The following example specifies an MTU of 1000 bytes:
Router(config)# interface serial 1Router(config-if)# mtu 1000Related Commands
encapsulation smds
Enables SMDS service on the desired interface.
ip mtu
Sets the MTU size of IP packets sent on an interface.
national bit
To set the E3 national bit in the G.751 frame used by the PA-E3 port adapter, use the national bit interface configuration command. To return to the default E3 national bit, use the no form of this command.
national bit {0 | 1}
no national bit
Syntax Description
Defaults
0 national bit
Command Modes
Interface configuration
Command History
Usage Guidelines
The national bit command sets bit 12 in the E3 frame.
To verify the national bit configured on the interface, use the show controller serial EXEC command.
Examples
The following example sets the national bit to 1 on the PA-E3 port adapter in slot 1, port adapter slot 0, interface 0:
Router(config)# interface serial 1/0/0Router(config-if)# national bit 1Related Commands
Sets the E3 international bit in the G.751 frame used by the PA-E3 port adapter.
Displays information that is specific to the interface hardware.
nrzi-encoding
To enable nonreturn-to-zero inverted (NRZI) line-coding format, use the nrzi-encoding interface configuration command. To disable this capability, use the no form of this command.
nrzi-encoding [mark]
no nrzi-encoding
Syntax Description
Defaults
Disabled
Command Modes
Interface configuration
Command History
10.0
This command was introduced.
11.3
The mark keyword was added for the Cisco 7200 series routers and Cisco 7500 series routers.
Usage Guidelines
All FSIP, PA-8T, and PA-4T+ interface types support nonreturn-to-zero (NRZ) and NRZI format. This is a line-coding format that is required for serial connections in some environments. NRZ encoding is most common. NRZI encoding is used primarily with EIA/TIA-232 connections in IBM environments.
Examples
The following example configures serial interface 1 for NRZI encoding:
Router(config)# interface serial 1Router(config-if)# nrzi-encodingThe following example configures serial interface 3/1/0 for NRZI mark encoding:
Router(config)# interface serial 3/1/0Router(config-if)# nrzi-encoding markphysical-layer
To specify the mode of a slow-speed serial interface on a router as either synchronous or asynchronous, use the physical-layer interface configuration command. To return the interface to the default mode of synchronous, use the no form of this command.
physical-layer {sync | async}
no physical-layer
Syntax Description
sync
Places the interface in synchronous mode. This is the default.
async
Places the interface in asynchronous mode.
Defaults
Synchronous mode
Command Modes
Interface configuration
Command History
Usage Guidelines
This command applies only to low-speed serial interfaces available on Cisco 2520 through 2523 routers.
If you specify the no physical-layer command, you return the interface to its default mode (synchronous).
In synchronous mode, low-speed serial interfaces support all interface configuration commands available for high-speed serial interfaces, except the following two commands:
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•
When placed in asynchronous mode, low-speed serial interfaces support all commands available for standard asynchronous interfaces.
When you enter this command, it does not appear in the output of more system:running-config and more nvram:startup-config commands because the command is a physical layer command.
Examples
This example changes a low-speed serial interface from synchronous to asynchronous mode:
Router(config)# interface serial 2Router(config-if)# physical-layer asyncRelated Commands
port
To enable an interface on a PA-4R-DTR port adapter to operate as a concentrator port, use the port interface configuration command. To restore the default station mode, use the no form of this command.
port
no port
Syntax Description
This command has no arguments or keywords.
Defaults
Station mode
Command Modes
Interface configuration
Command History
Usage Guidelines
By default, the interfaces of the PA-4R-DTR operate as Token Ring stations. Station mode is the typical operating mode. Use this command to enable an interface to operate as a concentrator port.
Examples
The following example configures the PA-4R-DTR ports to operate in concentrator mode on a Cisco 7000 series router:
Router# configure terminalRouter(config)# interface tokenring 3/0/0Router(config-if)# portpos ais-shut
To send the line alarm indication signal (LAIS) when the POS interface is placed in any administrative shut down state, use the pos ais-shut interface configuration command.
pos ais-shut
Syntax Description
This command has no keywords or arguments.
Defaults
No LAIS is sent.
Command Modes
Interface configuration
Command History
Usage Guidelines
In Automatic Protection Switching (APS) environments, LAIS can be used to force a protection switch. This command forces an APS switch when the interface is placed in administrative shut down state.
For more information on APS, refer to the "Configuring Serial Interfaces" chapter in the Cisco IOS Interface Configuration Guide.
There is not a no form of this command.
Examples
The following example forces the alarm indication on the POS OC-3 interface 0 in slot 3:
Router(config)# interface pos 3/0Router(config-if)# shutdownRouter(config-if)# pos ais-shutpos flag
To set the SONET overhead bytes in the frame header to meet a specific standards requirement or to ensure interoperability with another vendor's equipment, use the pos flag interface configuration command. To remove the setting of the SONET overhead bytes, use the no form of this command.
pos flag {c2 | j0 | s1s0} value
no pos flag {c2 | j0 | s1s0} value
Syntax Description
Defaults
The default c2 value is 0xCF, and the default sls0 value is 0.
Command Modes
Interface configuration
Command History
11.2 GS
This command was introduced to support the Cisco 12000 series Gigabit Switch Routers.
Usage Guidelines
Use the following values to tell the SONET transmission equipment the payload type:
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•
•
•
Examples
The following example sets the path signal identifier used to identify the payload content type to ATM on the pos interface in slot 9:
Router(config)# interface pos 9/0Router(config-if)# pos flag c2 0x13Router(config-if)# endRouter#pos framing
To specify the framing used on the POS (Packet-over-SONET) interface, use the pos framing interface configuration command. To return to the default SONET STS-3c framing mode, use the no form of this command.
pos framing {sdh | sonet}
no pos framing
Syntax Description
sdh
Selects SDH STM-1 framing. This framing mode is typically used in Europe.
sonet
Selects SONET STS-3c framing. This is the default.
Defaults
SONET STS-3c framing
Command Modes
Interface configuration
Command History
Examples
The following example configures the interface for SDH STM-1 framing:
Router(config)# interface pos 3/0Router(config-if)# pos framing-sdhRouter(config-if)# no shutdownRelated Commands
pos framing-sdh
The pos framing command replaces this command.
pos internal-clock
The clock source (interface) command replaces this command. Refer to the description of clock source command for information on transmit clock source.
pos report
To permit selected SONET alarms to be logged to the console for a POS interface, use the pos report interface configuration command. To disable logging of select SONET alarms, use the no form of this command.
pos report {b1-tca | b2-tca | b3-tca | lais | lrdi | pais | plop | prdi | rdool | sd-ber | sf-ber | slof | slos}
no pos report {b1-tca | b2-tca | b3-tca | lais | lrdi | pais | plop | prdi | rdool | sd-ber | sf-ber | slof | slos}
Syntax Description
Defaults
The following alarms are reported by default:
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•
•
•
•
•
•
Command Modes
Interface configuration
Command History
Usage Guidelines
Reporting an alarm means that the alarm can be logged to the console. Just because an alarm is permitted to be logged does not guarantee that it is logged. SONET alarm hierarchy rules dictate that only the most severe alarm of an alarm group is reported. Whether an alarm is reported or not, you can view the current state of a defect by checking the "Active Defects" line from the show controllers pos command output. A defect is a problem indication that is a candidate for an alarm.
For B1, the bit interleaved parity error report is calculated by comparing the BIP-8 code with the BIP-8 code extracted from the B1 byte of the following frame. Differences indicate that section level bit errors have occurred.
For B2, the bit interleaved parity error report is calculated by comparing the BIP-8/24 code with the BIP-8 code extracted from the B2 byte of the following frame. Differences indicate that line level bit errors have occurred.
For B3, the bit interleaved parity error report is calculated by comparing the BIP-8 code with the BIP-8 code extracted from the B3 byte of the following frame. Differences indicate that path level bit errors have occurred.
PAIS is sent by line terminating equipment (LTE) to alert the downstream path terminating equipment (PTE) that it has detected a defect on its incoming line signal.
PLOP is reported as a result of an invalid pointer (H1, H2) or an excess number of new data flag (NDF) enabled indications.
SLOF is detected when a severely error framing (SEF) defect on the incoming SONET signal persists for 3 ms.
SLOS is detected when an all-zeros pattern on the incoming SONET signal lasts 19 plus or minus 3 microseconds or longer. This defect might also be reported if the received signal level drops below the specified threshold.
To determine the alarms that are reported on the interface, use the show controllers pos command.
Examples
The following example enables reporting of SD-BER and LAIS alarms on the interface:
Router(config)# interface pos 3/0/0Router(config-if)# pos report sd-berRouter(config-if)# pos report laisRouter(config-if)# endRouter#Related Commands
Defines the IP addresses of the server, configures an interface type, and enters interface configuration mode.
Displays information about the POS controllers.
pos scramble-atm
To enable SONET payload scrambling on a POS interface, use the pos scramble-atm interface configuration command. To disable scrambling, use the no form of this command.
pos scramble-atm
no pos scramble-atm
Syntax Description
This command has no keywords or arguments.
Defaults
Scrambling is disabled
Command Modes
Interface configuration
Command History
Usage Guidelines
SONET payload scrambling applies a self-synchronous scrambler (x43+1) to the Synchronous Payload Envelope (SPE) of the interface to ensure sufficient bit transition density. Both ends of the connection must use the same scrambling algorithm. When enabling POS scrambling on a VIP2 POSIP on the Cisco 7500 series that has a hardware revision of 1.5 or higher, you can specify CRC 16 only (that is, CRC 32 is currently not supported).
To determine the hardware revision of the POSIP, use the show diag command.
To determine whether scrambling is enabled on the interface, use the show interface pos command or more nvram:startup-config command.
Note
Examples
The following example enables scrambling on the interface:
Router(config)# interface pos 3/0Router(config-if)# pos scramble-atmRouter(config-if)# no shutdownRouter(config-if)# endRouter#Related Commands
pos threshold
To set the BER threshold values of the specified alarms for a POS interface, use the pos threshold interface configuration command. To return to the default setting, use the no form of this command.
pos threshold {b1-tca | b2-tca | b3-tca | sd-ber | sf-ber} rate
no pos threshold {b1-tca | b2-tca | b3-tca | sd-ber | sf-ber} rate
Syntax Description
Defaults
The default rate is 6 for b1-tca, b2-tca, b3-tca, and sd-ber.
The default rate is 3 (10e-3) for sf-ber.
Command Modes
Interface configuration
Command History
Usage Guidelines
For B1, the bit interleaved parity error report is calculated by comparing the BIP-8 code with the BIP-8 code extracted from the B1 byte of the following frame. Differences indicate that section level bit errors have occurred.
For B2, the bit interleaved parity error report is calculated by comparing the BIP-8/24 code with the BIP-8 code extracted from the B2 byte of the following frame. Differences indicate that line level bit errors have occurred.
For B3, the bit interleaved parity error report is calculated by comparing the BIP-8 code with the BIP-8 code extracted from the B3 byte of the following frame. Differences indicate that path level bit errors have occurred.
SF-BER and SD-BER are sourced from B2 BIP-8 error counts (as is B2-TCA). However, SF-BER and SD-BER feed into the APS machine and can lead to a protection switch (if APS is configured).
B1-TCA, B2-TCA, and B3-TCA do nothing more than print a log message to the console (if reports for them are enabled).
To determine the BER thresholds configured on the interface, use the show controllers pos command.
Examples
The following example configures thresholds on the interface:
Router(config)# interface pos 3/0/0Router(config-if)# pos threshold sd-ber 8Router(config-if)# pos threshold sf-ber 4Router(config-if)# pos threshold b1_tca 4Router(config-if)# endRouter#Related Commands
posi framing-sdh
The pos framing command replaces this command.
pri-group
To specify ISDN Primary Rate Interface (PRI) on a channelized E1 or T1 card on Cisco 7500 series router, use the pri-group controller configuration command. To remove the ISDN PRI, use the no form of this command.
pri-group [timeslots range]
no pri-group
Syntax Description
Defaults
Disabled
Command Modes
Controller configuration
Command History
Usage Guidelines
When you configure ISDN PRI, you must first specify an ISDN switch type for PRI and an E1 or T1 controller.
Examples
The following example specifies ISDN PRI on T1 slot 1, port 0:
Router# isdn switch-type primary-4essRouter(config)# controllers t1 1
